Cobalt Chromium Toxicity Resource Center

Metal on Metal Hip Prostheses and Total Hip Arthroplasty Effects on Auditory and Visual Health





In the United States, there are over half a million patients implanted with metal on metal (MOM) hip prostheses. The typical elements released by the metal on metal hip prostheses are cobalt and chromium. The normal levels of cobalt and chromium within the body are below a microgram per liter of blood, or below a part per billion. The term microgram per liter is analogous to parts per billion. There are studies demonstrating that a normal range is within 0.1 to 0.3 micrograms per liter. According to this study, patients with well functioning MOM hips, had cobalt-chromium blood levels between 1.5 and 2.3 micrograms per liter. This is ten times higher than normal physiological levels and significantly contributes to the potential for cobalt-chromium toxicity, or metallosis. In association with metallosis, the study indicates that failure with prostheses was connected to visual and auditory issues resulting from elevated cobalt-chromium levels. There is a strong correlation between device failure with visual and auditory dysfunction.

In addition to the aforementioned findings, the study determines whether or not chronic low levels of metal exposure result in obvious physiological effects on the auditory and visual systems as well. In order to determine the effects of chronic low levels of cobalt-chromium, participants met with both an otolaryngologist and an ophthalmologist in order to determine primary or pre-existing pathologies within the ears and eyes, respectively. Subjects then underwent objective and subjective audiometric testing in order to assess auditory health and function. Similarly, the subjects demonstrated their visual health and functioning via subjective and objective visual testing. There were two types of participants in this study: those with MOMHR and those with total hip arthroplasty (THA). The participants in this study were then separated into groups based on their age and time since surgery. The participant’s blood tests also revealed that those with MOMHR had a blood, plasma, urinary cobalt and chromium levels that were 5 to 10 times higher than the THA participants. In terms of objective audiometric and visual findings between the MOMHR and THA groups, there was no observable difference, and patients in each group had similar auditory and visual function.

There is no conceivable evidence between MOMHR and altered brain stem responses for patients with exposure to chronic low metal levels. However, there is optic nerve atrophy (damage) in patients with exposure to high metal levels in their system  which reflects visual loss among this specific population. Whereas patients with long term exposure to low metal levels had no obvious association with auditory or visual defects, the patients with malfunctioning hip prostheses and elevated metal levels (up to hundreds in micrograms per liter) suggested visual and auditory defects.

Source: Auditory and Visual Health after Ten Years of Exposure to Metal-on-Metal Hip Prostheses: A Cross-Sectional Study Follow Up http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0090838

 


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